Separating crude oil
Fran Scott explains fractional distillation - the separation of crude oil into fractions
In fractional distillation a mixture of several substances, such as crude oil, is distilled and the evaporated components are collected as they condense at different temperatures. is used to separate Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms. into simpler, more useful Two or more substances that are not joined together. The substances can be elements, compounds, or both.. This method can be used because different A compound that contains hydrogen and carbon only. have different The temperature at which a substance rapidly changes from a liquid to a gas..
Fractional distillation
During the fractional distillation of crude oil:
- heated crude oil enters a tall Piece of apparatus in which mixtures separate during fractional distillation., which is hot at the bottom and gets cooler towards the top
- Vapour is a cloud of liquid particles. Steam is water vapour. from the oil rise through the column
- vapours A change of state in which gas becomes liquid by cooling. when they become cool enough
- liquids are led out of the column at different heights
Small hydrocarbon molecules have weak Weak attractive forces between molecules. When a simple molecular substance melts or boils, it is the intermolecular forces that are broken (not the covalent bonds in each molecule)., so they have low boiling points. They do not condense, but leave the column as gases. Long hydrocarbon molecules have stronger intermolecular forces, so they have high boiling points. They leave the column as hot liquid bitumen.
Crude oil fractions
The different, useful mixtures are called In fractional distillation, such as that of crude oil, the different parts of the original mixture are called fractions. The substances in each fraction have similar boiling points to each other.. This is because they are only part of the original crude oil.